U.S. patent number 3,869,658 [Application Number 05/398,406] was granted by the patent office on 1975-03-04 for direct curent supply with ribble suppression.
This patent grant is currently assigned to Telefunken Compter GmbH. Invention is credited to Martin Hanke, Hans Stiefken.
United States Patent |
3,869,658 |
Hanke , et al. |
March 4, 1975 |
DIRECT CURENT SUPPLY WITH RIBBLE SUPPRESSION
Abstract
A circuit arrangement for supplying a direct current, which is
free from interruptions, from an alternating line current. The
circuit includes: a first rectifier which initially rectifies the
line current; an energy store, which helps compensate for
variations in the rectified voltage; an inverter for chopping up
the recitified voltage; a transformer; a second rectifier
arrangement; a smoothing filter; and a control device. The voltage
which is generated at the output of the smoothing filter is fed to
the direct current load. When the voltage across the direct current
load falls below a rated value, a first electrical switching device
provides an extra current to the direct current load. On the other
hand, when the voltage across the direct current load increases
above the rated value, a second electrical switching device diverts
a portion of the current through the direct current load. In this
manner, any changes in the current and voltage across the load are
compensated.
Inventors: |
Hanke; Martin (Constance,
DT), Stiefken; Hans (Constance, DT) |
Assignee: |
Telefunken Compter GmbH
(Kanstanz, DT)
|
Family
ID: |
5857044 |
Appl.
No.: |
05/398,406 |
Filed: |
September 18, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Sep 22, 1972 [DT] |
|
|
2246505 |
|
Current U.S.
Class: |
363/15;
363/25 |
Current CPC
Class: |
H02M
3/285 (20130101); G05F 1/62 (20130101) |
Current International
Class: |
H02M
3/24 (20060101); G05F 1/10 (20060101); G05F
1/62 (20060101); H02M 3/28 (20060101); H02m
001/14 () |
Field of
Search: |
;321/1,2,4,10,18,19,27R
;323/23,25 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Beha, Jr.; William H.
Attorney, Agent or Firm: Spencer & Kaye
Claims
1. In a circuit arrangement for supplying an interruption-free
current for a direct current load, the arrangement including a
first rectifier, connected to receive an alternating supply
voltage, for rectifying the supply voltage; an energy store coupled
to the output of the first rectifier for storing the rectified
voltage; inverting means with phase cut control for chopping up the
rectified voltage into an alternating voltage; a transformer with a
primary winding coupled to the inverting means for receiving the
chopped voltage and a first secondary winding with both the primary
and secondary windings having center taps; a second rectifier
coupled to the first secondary winding of the transformer for
rectifying the chopped voltage; a smoothing filter coupled to the
output of the second rectifier and having its output connected to
the direct current load; and control means for monitoring the
current and voltage values at the direct current load and for
controlling the inverting means in dependence upon these values;
the improvement comprising: first electrical switching means
coupled to the output of said control means and connected for
providing an extra current to said direct current load in response
to control signals received from said control means when the
voltage across said direct current load falls below a rated value;
and second electrical switching means coupled to the output of said
control means and connected for diverting a portion of the current
through said direct current load in response to control signals
received from said control means when the voltage across said
direct current load increases
2. A circuit arrangement as defined in claim 1 wherein said first
electrical switching means is a series voltage regulator and said
second
3. A circuit arrangement as defined in claim 2 wherein said series
regulator includes a first transistor having its base coupled to an
output of said control means such that said first transistor is
switched into its conductive state in dependence upon the current
and voltage values monitored by said control means and said shunt
regulator includes a second transistor having its base coupled to
an output of said control means such that said second transistor is
switched into its conductive state in dependence upon the current
and voltage values monitored by said control
4. A circuit arrangement as defined in claim 3, further comprising
an auxiliary voltage source; and wherein: said first transistor of
said series regulator has its collector-emitter path coupled
between the output of said auxiliary voltage source and said direct
current load such that when said first transistor is switched into
its conductive state by said control means, said auxiliary source
supplies current into said direct current load; and said second
transisttor of said shunt regulator has its collector-emitter path
connected in parallel with said direct current load such that when
said second transistor is switched into its conductive state by
said control means, it diverts a portion of the current through
said direct current load and produces a voltage drop across a
resistance network formed by said inverter, said transformer and
said second rectifier so as to reduce the output voltage across
said direct current
5. A circuit arrangement as defined in claim 4 wherein said
auxiliary voltage source comprises a second secondary winding
inductively coupled with said primary winding of said transformer
and a third rectifier coupled between the output of said second
secondary winding and said
6. A circuit arrangement as defined in claim 2 wherein said series
voltage regulator includes a switching regulator having a switching
transistor and an inductor.
Description
BACKGROUND OF THE INVENTION
The present invention involves a device for converting an
alternating current into a direct current.
Electrical energy is most commonly generated in the form of a
three-phase alternating current. A portion of this generated
energy, however, is required for supplying direct current loads
and, therefore, there exists a heavy demand for conversion devices,
such as rectifier circuits, which are able to transform the
alternating current into a direct current. Such rectifier circuits
primarily consist of a transformer having a primary winding to
which the alternating current is applied and rectifier components
connected to the secondary winding of the transformer, where the
rectifier components allow the current to flow in only one
direction.
Such rectifier circuits, which are generally utilized in forming
direct current supply devices, can also include, in addition to
those elements mentioned above, circuitry for smoothing the
transformed and rectified direct current and a control device for
monitoring the electrical parameters of current and voltage applied
to the direct current load.
The outputs of the control device are connected to the primary
circuit of the transformer. The control device provides feedback
control signals to the primary circuit in response to changes in
the electrical parameters as a result of fluctuations in the direct
current load in order to compensate for such fluctuation so that a
reasonably constant current and voltage are generated at the direct
current load itself.
A further step in the development of such known direct current
supply devices was the introduction of a static inverter. In such a
known arrangement of the direct current supply device, the
alternating line current is initially rectified. The resulting
direct voltage is then chopped up, in response to control signals
from the control device which depend on the electrical parameters
at the direct current load, and the resulting alternating voltage
signals are transformed and are again rectified. The double
rectification and particularly the chopping up of the direct
voltage obtained from the alternating current supply in the first
rectifier arrangement, which includes an energy store to which the
direct voltage is fed, already assures a relatively good quality
for the electrical parameters applied to the direct current
load.
The present invention relats to a circuit arrangement for supplying
a current/voltage controlled current without interruptions to a
direct current load. This type of circuit arrangement generally
includes: a first rectifier arrangement for rectifying an
alternating current supply; an energy store in which the direct
voltage obtained from the alternating current supply is stored; an
inverter circuit with phase switching control with which the direct
voltage present at the energy store is chopped up; a transformer
with center tapped primary and secondary windings; a second
rectifier arrangement in which the transformed alternating voltage
is rectified; at least one smoothing filter; and a control device
for monitoring the electrical output values applied to the direct
current load and for controlling the operation of the inverter
circuit in dependence on the output values. Even with such an
arrangement, however, there is still smoe residual ripple in the
generated direct voltage.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved
circuit arrangement of the above-mentioned type so that the
residual ripple still present in a direct voltge generated with the
known circuit arrangements can be sufficiently eliminated.
Another object of the present invention is to achieve this result
while requiring an amount of additional energy which is so small as
to create a negligible reduction in the total power efficiency of
the circuit arrangement.
These objectives are accomplished by providing an electrical
switching device in the circuit arrangement, which device
cooperates with the control unit to compensate for fluctuations so
as to assure a constant current and voltage at the direct current
load. For this purpose, the electrical switching device either
supplies an extra current to the direct current load which has a
predetermined amplitude/time characteristic or produces a voltage
drop at the resistance network formed by the inverter, the
transformer and the second rectifier arrangement, thereby drawing
off a portion of the current from the direct current load. Thus, in
accordance with the circuit arrangement of the present invention,
the already regulated direct current through the direct current
load is readjusted in that either an additional current is fed to
the already regulated direct current load which current corresponds
to the deviation between the actual and the rated current or a
corresponding current is withdrawn from the direct current load via
the voltage drop produced at the internal resistance of the circuit
arrangement.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic circuit diagram of one embodiment of the
circuit arrangement of the present invention.
FIG. 2a is a circuit diagram of a first embodiment of the
electrical switching device according to the present invention for
eliminating the residual ripple.
FIG. 2b is a circuit diagram of a second embodiment of the
electrical switching device according to the present invention for
eliminating the residual ripple.
FIGS. 3 a-g are waveform diagrams of the voltages produced at
various points in the circuit arrangement according to the present
invention with an indication of the switching times for the
electrical switching device responsible for the elimination of the
residual ripple.
FIGS. 4a-d are waveform diagrams of the development of the
amplitude/time curve of the current to be fed to the direct current
load which results from the voltage drop at the resistance network
upon a sudden change in current which occurs due to a fluctuation
in the load at the direct current load.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 1, a line transformer 1 receives, for example, the
three phases R, S, T of a three-phase line current. The phase
currents are individually rectified and smoothed in a first
rectifier arrangement 2, so that a direct voltage V.sub.B appears
at the output of the first rectifier arrangement 2. This direct
voltage V.sub.B is fed to a buffer battery 3 which acts as an
energy store and serves to help compensate for fluctuations in the
line current. Even if the line current should cease altogether,
this buffer battery would go into action and maintain emergency
operation for a given period of time thereby enabling at least the
performance of certain protective measures for emergency operation
of a direct current load 14.
The direct voltage V.sub.B applied to the buffer battery 3 is now
converted into an alternating voltage by an inverter arrangement.
The inverter includes controllable electronic switching elements 4,
5 which lie in the primary winding circuit 6 of a transformer. By
regulating the moment at which these controllable electronic
switching elements 4, 5 are actuated it is also possible to
control, simultaneously with the chopping up of the direct voltage
V.sub.B, the signal amplitude in dependence upon the output value
of the output voltage V.sub.A at the direct current load 14, i.e.
the electronic switching elements can phase cut controlled. A
control unit 13 generates control pulses which are dependent upon
the output value at direct current load 14 and have a fixed, given
repetition frequency of, for example, 20 kHz. The duration of the
control pulses in order to provide the desired phase cut, or
switching, control, will be varied so as to correspond to the
respective actual output values.
The amplitude of the average voltage output produced by the
switching elements 4 and 5 from the alternating line voltage can be
varied by controlling the point of time during each forward voltage
half-cycle at which each of the switching elements 4, 5 is switched
into its conductive state. By providing during each half-cycle of
operation, an appropriate phase regulating for supplying an
activating signal to the respective switching element, the element
will only be switched into its conductive state for a portion of
its respective half-cycle. By varying the time of conduction of the
switching element in this manner, the average output -voltage of
the rectifier 8, 9, accordingly, can be varied. Such operation of
the switching elements of the rectifier is referred to herein as
phase cutting control and can be utilized for compensating for
variations in the alternating line voltage and for slow variations
of the direct current load.
The controllable electronic switching elements 4, 5 disposed in the
primary circuit 6 of the transformer may be constituted by
transistors as well as thyristors which are alternately switched
into their conductive state by the control unit 13 in
correspondence with the output value dependent control pulses.
When transistors are used for the electronic switching elements,
they are connected via their bases with the appropriate outputs of
the control unit 13 and at their collectors with one pole, for
example the positive pole, of the buffer battery 3. The emitter
terminals of the transistors are each connected with respectively
opposite ends of the primary winding 6 of the transformer. The
center tap of the transformer is connected to the other pole, for
example the negative pole, of the buffer battery.
When thyristors are used for the electronic switching elements, the
cathode terminals of the thyristors are generally connected with
the ends of the primary winding 6 of the transformer. The anode
terminals are connected with, for example, the positive pole of the
buffer battery. The thyristors are controlled at their gates by the
control unit 13 so that each control pulse from control unit 13
puts one of the thyristors into its conductive state. At the end of
each control pulse, the current flowing through the thyristor must
be interrupted.
The alternating voltage across the primary winding 6 is transformed
to the secondary winding 7, in correspondence with the ratio of the
number of windings in each.
The secondary winding 7 of the transformer also has a center tap
and furnishes the transformed alternating current to a second
rectifier arrangement. This second rectifier arrangement includes
two diodes 8, 9 which are each connected at their anodes with a
respective one of the ends of the secondary winding 7. The cathode
terminals of the diodes 8, 9 are connected together. The direct
voltage for the direct current load 14 is that voltage which
appears between the common cathode point and the center tap of the
secondary winding 7 of the transformer.
The direct voltage is smoothed via a smoothing filter, which
includes inductive and/or capacitive smoothing elements 10, 11, 12
so that any residual ripple in the voltage is limited to about only
1 percent of the absolute value.
The first and second rectifier arrangements can also be realized by
a bridge circuit.
The values of the electrical output current I.sub.A and voltage
V.sub.A present at the direct current load 14 are monitored in the
control unit 13 where they are compared with corresponding rated
values with respect to both their absolute value and quality.
Deviations that do occur are compensated for by the appropriate
variation in the phase cut control.
In order to be able to compensate for any remaining ripple in the
direct voltage and possibly also any sudden changes in the load of
the direct current load without any delays, the circuit arrangement
of the present invention includes an electrical switching device
which, depending on the polarity of the deviation of the voltage
and current at the output from the rated values or the change in
the load, supply current to the direct current load or remove
current therefrom, by producing a voltage drop at the resistance
network.
The primary purpose of the electrical switching device provided by
the present invention is to counteract decreases or increases in
the current flowing in the direct current load. For this purpose,
the present invention utilizes a combination of a series regulator
and a parallel regulator. The series regulator is provided to
compensate for decreases in the load current and the parallel
regulator is provided to compensate for increases in the load
current. The circuit arrangement according to the present invention
of the series and parallel regulators has the particular advantage
of providing substantially immediate compensations for a sudden
change in the load. Thus, with such an arrangement, it is not
necessary to wait out the reaction time of the phase cutting
control in the primary circuit of the transformer in order to
obtain compensation of any sudden change in the direct voltage at
the output.
In the schematic circuit diagram shown in FIG. 1, the electrical
switching device is shown as a set of switches 15 and 16, which are
controlled by the control unit 13. The series regulator is
represented by switch 15 and the shunt regulator by switch 16.
If a deviation of the direct output voltage from the arithmetic
mean value (rated value) toward higher values is noted in the
control unit 13, then the switching path of the shunt regulator 16
is closed in order to reduce the excess voltage and current. Thus a
portion of the current flowing from the cathode terminal of diodes
8, 9 to the direct current load 14 is diverted, while the voltage
V.sub.A at the direct current load 14 remains constant.
If the control unit 13 detects a deviation of the direct voltage at
the output toward lower values, the control path of the series
regulator 15 is closed. Upon closing the path of the series
regulator, the circuit of an auxiliary voltage source 17 is closed
which thus is able to transmit energy to the direct current load
14. The current, therefore, is fed into the direct current load 14
via this auxiliary voltage source 17. The auxiliary voltage source
17 is coupled between the center tap of the secondary winding 7 of
the transformer and the switch 15 of the series regulator.
The control unit 13 includes, as shown in FIG. 1, a reference
voltage V.sub.ref and two operational amplifiers, which compare the
output voltage V.sub.A with the reference voltage V.sub.ref and
which produces a pair of output signals for controlling either the
series regulator 15 or the shunt regulator 16. Furthermore the
control unit 13 includes a pulse generator, which is controlled by
the output signals of said operational amplifiers and which
supplies the switching elements 4, 5 with said control pulses,
which are responsible for the phase cutting control. The control
means for controlling the output current I.sub.A are not shown in
detail, because they may be realized in a manner analogous to that
for controlling the output voltage.
Two alternative embodiments of the auxiliary voltage source 17 are
illustrated in FIGS. 2a and 2b. The auxiliary voltage source
includes a third rectifier arrangement, which has two diodes 18,
19. The diodes 18, 19 are each connected at their anodes with
respectively opposite ends of another secondary winding 7' which is
magnetically coupled with the primary winding 6 of the transformer.
The cathode terminals of diodes 18, 19 are connected together so
that a direct voltage is produced. Their output and this direct
voltage are smoothed by inductive and/or capacitive smoothing
elements 20, 21. This smoothed direct voltage is then fed to the
series regulator 15.
In accordance with the embodiment shown in FIG. 2a, the series
regulator is realized by an npn transistor 151, which is controlled
at its base by the control unit 13. When transistor 151 is switched
into its conductive state, a direct output current is fed into the
direct current load 14 via the collector-emitter path of this
transistor 151.
The shunt regulator 16, in the embodiment of FIG. 2a, is also
realized by an npn transistor 161, which is also controlled at its
base by the control unit 13, in the same manner as the transistor
151 of the series regulator. Transistor 161 of the shunt regulator
has its collector-emitter path connected in parallel with the
direct current load, with its collector also being connected, via
the inductive and/or capacitive smoothing elements 10, 11, 12, with
the common cathode terminal of diodes 8, 9 of the second rectifier
arrangement and its emitter with the center tap of the secondary
winding 7 of the transformer. When the transistor 161 is switched
into its conductive state, current is diverted from the direct
current load 14, via the collector-emitter path of transistor 161
of the shunt regulator so as to compensate for any possible excess
voltage across the direct current load 14.
FIG. 2b shows another embodiment according to the present
invention, which differs from that shown in FIG. 2a only by the
different realization of the series regulator. The series regulator
is here realized by a so-called switching regulator which draws
current from the auxiliary voltage source with a high direct
voltage, which is formed in the same manner as shown in FIG. 2a.
The transistor 152 is also controlled at its base by control unit
13. When the transistor is switched into its conductive state,
however, it does not directly affect the direct current load 14,
but instead supplies current to an inductance 23 which then
transmits its energy to the direct current load 14. A capacitor 24
is arranged in parallel with the direct current load 14 and thus
also with the shunt regulator 161. This capacitor 24 together with
inductance 23 forms a filter. If the direct output voltage at the
direct current load 14 drops below the rated value, energy is first
taken from capacitor 24 before the current flowing through
transistor 152, when it is switched into its conductive state,
becomes effective. The cathode terminal of a diode 22 is connected
with the connecting point of the emitter terminal of the switching
transistor 152 and the inductance 23 and the anode terminal of this
diode 22 is connected with the line leading to the center tap of
the secondary winding. The diode 22 permits the current to continue
to flow even when transistor 152 is blocked.
A primary requirement with respect to both the series and shunt
regulators in accordance with the present invention as illustrated
in detail in FIGS. 2a and 2b, is that it must be possible to
provide a linear amplification with the regulators. Thus, the
present invention is not limited to these particular embodiments,
rather other linear amplifying elements or circuits can also be
used if their operation is similar to that of the transistors.
The operation of the circuit arrangement according to the present
invention will be explained in detail with the aid of the diagrams
shown in FIGS. 3 and 4. The chopping frequency of the static
inverter has been selected, in order to simplify the illustrations,
to be equal to the frequency of the line supply. In practical
circuit arrangements, however, a substantially higher chopping
frequency is employed, which, as already mentioned, may be 20 kHz,
for example.
As shown in FIG. 3a, the three phases R, S, T of a three-phase line
voltage are shifted with respect to one another by 2/3.pi. and have
the voltage amplitudes .+-.V.sub.line. The phases are initially
full-wave rectified in the first rectifier arrangement, as shown in
FIG. 3b. The resulting direct voltage V.sub.B, whose average direct
voltage component is approximately 1.66 .sup.. V.sub.max (where
V.sub.max is the peak value of the three phases R, S, T), is fed to
the buffer battery and is chopped at a given constant repetition
frequency with the aid of the inverter elements 4 and 5.
The relationship of the control pulse sequences for the inverter
elements, with respect to one another, must follow the condition
that between each two control pulses for one of the elements there
must occur a control pulse for the other element. If one control
pulse with its subsequent pulse interval is considered as a unit of
time, the second sequence of control pulses must be shifted by
one-half a unit with respect thereto. The sequence of positive and
negative rectangular pulses, V.sub.Z, resulting from the inversion
and simultaneous phase cut control is shown in FIG. 3c.
This rectangular alternating voltage V.sub.z is now passed through
the transformer, as shown in FIG. 3d, and thereby is decreased in
amplitude, V.sub.Tr. The transformed voltage V.sub.Tr is rectified
in the second rectifier arrangement. Thus there results the
sequence of unipolar, for example positive, rectangular pulses,
V.sub.P, as shown in FIG. 3e.
After these pulses V.sub.P pass through the inductive and/or
capacitive smoothing elements, which are connected in series with
the second rectifier arrangement, there then results the direct
voltage shown in FIG. 3f, whose residual ripple is determined
primarily by the time constants of the inductance and capacitance
of the smoothing elements. Thus there appears at the output of the
circuit a direct voltage V.sub.A with a superimposed alternating
voltage which in a first approximation has a triangular shape. The
amplitude of this alternating voltage is a measure of the residual
ripple of the direct voltage at the output and is shown in FIG. 3f
by the reference marker .DELTA.V.sub.A.
The primary object of the present invention is to substantially
compensate for this residual ripple. For this purpose the present
invention provides a circuit arrangement which includes a
combination of a series regulator and a shunt regulator. As
explained above, the series regulator compensates for increases in
the load current and the shunt regulator compensates for reductions
in the load current. In order to illustrate this, the switch-on
times of the series and shunt regulators are indicated in FIG. 3g.
During the period in which the voltage V.sub.A lies below the rated
value, the series regulator is switched on and then feeds an
additional current into the direct current load so that the voltage
is raised to the rated value. If the voltage V.sub.A exceeds the
rated value, the control unit activates the shunt regulator so that
it produces with the additionally drawn current a voltage drop
across the resistance network formed by the transformer, the second
rectifier arrangement and the filter formed by the inductive and/or
capacitive smoothing elements, so that the excess voltage is
compensated out.
Furthermore, with the circuit arrangement according to the present
invention, it is possible to compensate for the fluctuations in the
voltage which occur when there is a sudden change in the direct
current load which thereby causes a corresponding sudden change in
the current. FIGS. 4a-d illustrate an example for the
amplitude/time curve of the compensating current flowing through
the series and shunt regulators when a sudden change in the load
current at the direct current load occurs.
The dashed curve in FIG. 4a shows the triangularly shaped
alternating voltage which fluctuates with its residual ripple
.DELTA.V.sub.a about the arithmetic mean of the direct output
voltage V.sub.A as shown by the dot-dash lines. This triangular
alternating voltage, however, is an idealized representation. The
currents of the series and shunt regulators, which are shown in
FIGS. 4b and 4c, act to compensate for the decrease or excess in
voltage at the direct current load, in the manner described above
in connection with FIG. 3. The current I.sub.L coming from the
series regulator is illustrated in FIG. 4b and the current I.sub.P,
which is to be compensated by the shunt regulator, is illustrated
in FIG. 4c. In FIGS. 4b and 4c, the solid lines illustrate the
necessary compensating currents when there is a sudden change in
the load while the dashed lines illustrate the necessary currents
when there is not such sudden change. The amplitude/time
relationship of currents I.sub.l or I.sub.P, respectively, and the
direct output voltage V.sub.A or its residual ripple are directly
associated with each other.
If at a time t.sub.1, the direct current load suddenly changes,
then a correspondingly sharp change would occur in the load current
flowing through the direct current load, as shown in FIG. 4d.
If the circuit arrangement was operated without the combination of
the series and shunt regulators as provided by the present
invention and the arrangement were left to fend for itself, the
voltage curve shown in a solid line in FIG. 4a would initially
result since the change in the load current, in accordance with the
energy laws, would cause the same sudden change in the direct
output voltage. Although this change would be eliminated by a
change in the phase cut control, there is a time delay before such
compensation is provided, with the period of the delay depending on
the system involved. The circuit arrangement according to the
present invention, however, permits an almost delay-free
compensation of the voltage fluctuations resulting from changes in
the load current.
At time t.sub.1, the series regulator becomes effective until the
momentary value of the direct output voltage has reached the rated
value. For the short time when there is excess voltage, the shunt
regulator becomes effective and then the series regulator takes
over again. The basic frequency for the control of the series and
shunt regulators would generally be of a higher repetition
frequency than that of the sequence of control pulses for the phase
cut control in the first rectifier arrangement.
The combination of the series and shunt regulators, as provided by
the present invention, permits a compensation of the residual
ripple in a direct voltage produced by the inversion and
rectification to an amount of .DELTA.V.sub.A which is approximately
1 mV. Any possible sudden changes in the direct current load also
can be compensated for with the arrangement of the present
invention almost without any delay and thereby assure high
continuity of the output values V.sub.A and I.sub.A.
An additional special advantage of the circuit arrangement
according to the present invention is that the series and shunt
regulators need to be dimensioned only to handle a portion of the
load current flowing through the current load.
It will be understood that the above description of the present
invention is susceptible to various modifications, changes and
adaptations and the same are intended to be comprehended within the
meaning and range of equivalents of the appended claims.
* * * * *